But it shows a marked leap in Smith's likely supporters. In August, a similar poll from Quinnipiac had Casey ahead by a margin of 18 percentage points.

The numbers pushed The Washington Post's "The Fix" blog to classify the Senate race as "lean Democratic," as opposed to "solid Democratic."

In responding to the news about the poll numbers, Larry Smar, Casey's campaign manager, said in an email to PA Independent that Smith's "divisive brand of politics is too extreme for Pennsylvania."

He dismissed anything conclusive about the polls.

"Public polls have been all over the place," Smar said. "Tom Smith has dumped millions of his personal fortune into attack ads. A lot of people don't yet know Tom Smith's record of founding a tea party group and pushing policies to dismantle Medicare in order to give more tax cuts for the wealthy."

The Smith campaign took advantage of the gains, releasing a statement touting the results. Smith "has clearly captured the momentum," said his campaign manager, Jim Conroy.

"Voters are rejecting Bob Casey's misleading negative attacks in favor of Tom's positive vision for the future and detailed plan to grow the economy and create jobs," said Conroy's statement.

Casey swung at Smith with a Sept. 12 ad introducing voters to "Tea Party Tom Smith," in which he chews out Smith's proposed policy changes.

"But is Tom Smith your cup of tea? He wants to privatize Social Security and end Medicare as we know it, making seniors pay $6,000 more all while giving even more tax breaks to the wealthy," the narrator says.